Vibration In B61

[graham1948]

Recently I purchased a 1963 B 613 S. It has a 250 C Turbo Motor coupled to a quad box connected to a diff that indicates that is is a 4.2 ratio diff. My problem is that I have a vibration that kicks in at fifth gear at speeds between 40 and 50 mph. I am told this could be a varitey of things including, wheel balance, worn universals, an out of balance tail shaft, or maybe the tail shaft is out by one on the splein. The universals appear to be OK and as I have fitted new tyres I think the problem is elsewhere. Tomorrow we will check the univerals again and make sure the tailshaft is aligned in the correct manner. Does anyone have anything else we can check? I am based in Gladstone Queensland Australia, my B Model was purchased new by Buntine Roadways in the Northern Territory in May 1963 and was fitted with a P motor and Duplex. My restoration is complete and next week I intended to drive it to a truck show 700 miles from where I live, but if I can't fix the vibration I might have to make other plans, as I am told that in some cases these vibrations could do severe damage to the bell housing. Any thoughts? Graham

[MACKS]

Do you have the drum type parking brake on the back of the tranny if so make sure it's not loose, I always had a problem with mine the bolt that holds the flange to the output shaft would loosen up and make it vibrate. You gotta push real hard up and down on the drum to see if it moves.

[graham1948]

I don't have the drum type handbrake she was converted to maxi brakes some yars ago. Graham

[HK Trucking]

I don't have the drum type handbrake she was converted to maxi brakes some yars ago. Graham

Whether the drum is still there or not, the driveshft yoke could be loose on the trans. out put shaft.

With the parking brake applied, wheels chocked, and the transmission in neutral, slide under the truck and push upward forcefully on the driveshaft near the back of the trans.

If there is up & down movement, try to determine if it's a loose U Joint, or if the yoke is loose on the output shaft spline.

Loose U joint must be replaced.

If the yoke is loose, then remove the U joint & drop the driveshaft to allow access to the retaining nut on the output shaft. Remove the cotter pin, then with at least a 3/4 drive impact wrench & suitable socket remove the retaining nut.

Check & clean the threads on the nut & shaft, then apply red loctite to the threads on the nut & shaft. Re install the nut & tighten the livin' sh*t out of it with the impact wrench,being sure to have a hole lined up with a slot in the nut so the cotter pin can be re installed.

(Some of the later model quad boxes used a retaining bolt instead of a nut, but the procedure is the same, just there's a bolt & a thick washer instead of a nut)

Reinstall the driveshaft.

This "looseness check" should also be performed at the other driveshaft yokes where they connect to the rear diffs.

If any of those are loose, they can be tightened the same way.

I have seen vibrations such as this caused by loose yokes quite a few times

Unless a driveshaft has obvious damage, or the U joints are out of time, it's more than likely a loose yoke or U joint.

[graham1948]

Many thanks for your help. Today we removed the front universal (previously it had checked out OK,i.e. no obvious movement) when we took it out we fount that one of the caps had damaged roller pins and this had caused scoring to the hard metal of the universal. We installed a new universal and we got a 60 to 70% improvement, but we still have a vibration that we can now drive through. It seems to go at about 50mph and is still there with the power off. My guys tell me that the vibration that is left is probably either whell bearings or out of balance tyres. It is the week end down here at the moment so on Monday we will check out the whell bearing and replace any suspect ones and then take her to someone to have the wheels balanced. I though my 4.2 ratio rear end might get me up to 65 mph but a friend travelling behind me this morning tell me I was topping out at 48mph. Too bloody slow! When I get everything balanced up I am hoping to get at least 60 to 65mph. If not I am going to have to find a faster diff. Again many thanks for the advice. Graham

Many thanks for your help. Today we removed the front universal (previously it had checked out OK,i.e. no obvious movement) when we took it out we fount that one of the caps had damaged roller pins and this had caused scoring to the hard metal of the universal. We installed a new universal and we got a 60 to 70% improvement, but we still have a vibration that we can now drive through. It seems to go at about 50mph and is still there with the power off. My guys tell me that the vibration that is left is probably either whell bearings or out of balance tyres. It is the week end down here at the moment so on Monday we will check out the whell bearing and replace any suspect ones and then take her to someone to have the wheels balanced. I though my 4.2 ratio rear end might get me up to 65 mph but a friend travelling behind me this morning tell me I was topping out at 48mph. Too bloody slow! When I get everything balanced up I am hoping to get at least 60 to 65mph. If not I am going to have to find a faster diff. Again many thanks for the advice. Graham

[Freightrain]

With single overdrive and 4.2 gears, 22" tires, you should get near 70 mph topped out on govenor. I get ~65 with 4.65 gears at 2100 rpm.

Hope you get the shake fixed.

[graham1948]

Many thanks to everyone who offered help with regard to the vibration in my B model. Member 261 nailed it. We found that we had movement in the yokes and in turn the retainer nut that holds the rear yoke onto the diff was loose causing severe up and down movement. We replaced the front and back universals and tighten up the retaining nuts and the vibration has gone. I have just returned from a 2000 mile trip in her towing a 10 ton van/trailer and she performed beautifully. Only trouble was we threw a fan belt and the air conditioner that we had installed stopped until we could fit the spare we were carrying (it is over 100 degrees in the shade over here at the moment, and at 58 years of age I am too soft to drive a B model without air conditioning). Water temp sat on 75 all the way and we held oil pressure at 75 also. She pulled up the hill like a trouper. The only thing I have to fix now is, we are getting engine oil into the air lines so we will get the compressor overhauled (not too much oil, she only used 2 pints for the whole 2000 miles), and I've got to get rid of the noise that sounds like 100 angry monkeys grinding ball bearings in the gearbox when in forth and fifth hi-split. She probably has not been driven in these gears for years because when I purchased her she was on a property and only used once in a while to pull timber out of the paddocks. No highway use at all. The noise did get a bit better by the time we got back this afternoon but it is still too loud. Any ideas? I will probably have to ultimately get the gearbox overhauled, but I understand that some people have been able to reduce this noise by thicker oil and additives. Although I said my diff was rated at 4.2 I couldn't get any more than 50 mph out of her and coming down the hills she appeared to hit the goverors at about 55 mph. Again many thanks for past help, and if you have any suggestions for the gearbox grinding noise I would appreciate it. Thanks Graham

[graham1948]

I've never done this before so I hope this picture of my B model gets through. Restoration was complete last week and since then we have completed 2000 miles in her with virtually now problems other than the ones I posted earlier and am looking for help with. Graham

I've never done this before so I hope this picture of my B model gets through. Restoration was complete last week and since then we have completed 2000 miles in her with virtually now problems other than the ones I posted earlier and am looking for help with. Graham

I've never done this before so I hope this picture of my B model gets through. Restoration was complete last week and since then we have completed 2000 miles in her with virtually now problems other than the ones I posted earlier and am looking for help with. Graham

I've never done this before so I hope this picture of my B model gets through. Restoration was complete last week and since then we have completed 2000 miles in her with virtually now problems other than the ones I posted earlier and am looking for help with. Graham

[HK Trucking]

Yup, it worked! Nice job!

Glad you got the vibration worked out.

I've got to get rid of the noise that sounds like 100 angry monkeys grinding ball bearings in the gearbox when in forth and fifth hi-split.

When I drove quad box equipped trucks I did notice that it seemed to be "the nature of the beast" to get a high pitched whine, almost like a siren, when in Hi split 4th & 5th. Not having heard the particular noise that yours is making, I don't know if that's what you're referring to, or if it's something worse.

Be sure to use a good quality 80w90 gear lube in your quad box.

In the past I have installed rubber hose over the shift levers to quiet some of that noise.

Just cut a piece of heater hose to the same length as each shift lever, remove the knobs, slide the heater hose over the levers, and replace the knobs.

As far as your top speed, is your engine reaching 2100 RPM's?

If not, check the throttle linkage to be sure it's pulling the pump all the wayopen against the stop.

If it is, then you may have to re adjust the hi idle screw to achieve 2100.

Do you have a TRQ7220 or a TRQ722?

With a TRQ 7220 that truck should fly with your stated rear end ratio of 4.2.

Even with a single overdrive quad box (TRQ722) it still should do better than 55 mph,with that rear end ratio, in my opinion.

[graham1948]

Thanks again for your input. I've got the whine as well and I can live with that. I drove a B model for five years on regular trucking work 35 years ago and I learnt to hide the whine a little by either holding onto the split gear lever or putting a strong rubber band around the two levers to stop the vibration a little. I realy think I have something a bit more, that's why I think it is either oil not getting to the top of the box properly or maybe there is some wear or something else that has caused the gears on four and fifth to rattle much more than normal. With regard to top speed, when I did the restoration I purchased a brand new rev counter and cable from Mack Trucks. It seemed to work fine for the first 1000 miles and then it went crazy and was reading all over the place. When it was working OK it indicated that I was topping out at about 18 to 1900 RPM. I am still not convinced I have a 4.2 ratio diff though, during her life time is it possible that someone has changed the diff for a lower speed one (although I don't know why someone would do that-but in her early working days she was used on road train work and it would not have been unusual for her to pull up to three fully loaded 35 foot trailers each with 20 ton of frieght on board). Even though the diff housing says 4.2 someone might have put a different ratio set up in her. Only way to find out I guess is to pull it out and count the teeth? Do you think it would be better first to get her on a professional dyno machine. Again, you help is appreciated. Graham

[HK Trucking]

When it was working OK it indicated that I was topping out at about 18 to 1900 RPM

I would say you should do whatever is necessary to get the RPM's up to 2100.

My Mack "Bible" calls for a no load high idle RPM of 2250 to 2310 on a T673C.

If you're getting 55MPH @ 1800 - 1900, you'll easily be up past 65 MPH once you get the high RPM up where it should be. Perhaps that would make the current rear axle ratio satisfactory.

Best of luck.

Herb

[graham1948]

Thanks Herb you've been most helpful. First of all I'll get someone here to do a genuine test on how many RPM she is delivering. If she is topping out at 1800 to 1900 I'll get them to make the necessary adjustments then we'll she what she will do before we play with the diff. The general consensis on the noise in the gearbox in forth and fifth hi-split is that we should first change the oil and she what happens. Regards Graham

[MACKS]

It sounds like the problem with your tranny is comeing from the back end of the box, you can remove the back end with out pulling the whole tranny, just disconect the linkege to the back and unbolt it pull it straight back, one thing to watch for is short peice of copper tube in the end of the main shaft dont loose it and when you put the tranny back togather dont use any siicone, thats what happened to mine a small peice found its way into the main shaft and pluged the oil hole under one of the gears. Also most of the whine you hear in the quad box comes from the berings on the back end of the out put shaft they must be ajusted right, if you have the back end rebult the tranny shop will set them up for you. Good Luck

[graham1948]

Well here I am back from the outback and another 1500 miles successfully completed in the old B model. I found out why she won't go over 48 miles per hour. She has a 7.48 ratio diff. I am desperately looking for a 6.36 or better, but they are as scarce as hens teeth down here. The noise in the gearbox is a lot better since we changed the oil and added some Morreys additive. We know have discovered we have a bad throw out bearing. It won't dis-engage, so it looks like the gearbox will have to come out, so whilst we are at it we may as well do the clutch and pressure plates at the same time. Anything else to look at while we are doing it? Our oil pressure at full operating temperature runs at a constant 75 psi, I am happy with that, but what should it be. She pulls her head off and I am extremely happy with the way she performs. We are pulling a pan with a gross weight of just 10 ton, so all up we gross about 16 tons. I will be in the States in a couple of months and I thought if I can't get a suitable diff over here I might be able to get one over there and ship it home. Is this possible and what do you think I would have to pay for a good unit or better still a remanufactured one? Regards Graham

[Bmoto1]

I bought a compete rear end from Dennis at www.oldmacks.com good luck